RU2716796C2 - Method for automatic odorization of natural gas and device for implementation thereof - Google Patents

Abstract

FIELD: oil, gas and coke-chemical industries.

SUBSTANCE: group of inventions relates to the gas industry and can be used at gas distribution stations for feeding the odorant into the gas stream in order to impart an odour to it. Method for automatic odorization of gas involves periodic filling of measuring container from vessel with odorant and subsequent emptying of high pressure gas in low pressure gas line on hydraulic line, upper point of which is located above level of liquid in supply container. High-pressure gas is fed into a special reference point on a hydraulic line dividing the fluid therein into two opposite streams flowing into the low-pressure gas line and returning to the waste container. Amount of odorant falling into low-pressure gas line is calculated by geometrical dimensions of part of hydraulic line from reference point to its filling level and temperature of odorant in it. Device for gas automatic gas odorization contains a capacity tank, a level indicator, a low-pressure gas line, on which there is a gas flow rate measurement unit, a gas reducer, an electromagnetic valve, a control unit, a hydraulic line connecting the supply tank to the low pressure gas line. Hydraulic line is equipped with a temperature sensor and a special reference point, into which high-pressure gas is supplied from the output of the electromagnetic valve. First input of the control unit is connected to the gas flow measurement unit, the second input is connected to the temperature sensor. Gas reducer inlet is connected to high-pressure source while its output is connected to solenoid valve. Upper point of the supply tank is connected to the outlet gas line through the second main line.

EFFECT: technical result is higher reliability of operation of method due to simplified design of device, as well as high accuracy of dosing liquid.

2 cl, 1 dwg

Description

The invention relates to methods and devices for proportional dosing, in particular to odorization of natural gases, and can be used in the gas industry at gas distribution stations to supply odorant to a gas stream in order to give it a smell.

A known method of gas odorization, implemented in a device containing a consumable container, a control unit and a metering device based on a normally closed two-way solenoid valve, through which the odorant can by gravity flow from the consumable container to the gas outlet of the gas distribution station (Gas odorizer OG-10A, Technological equipment catalog gas distribution stations of gas pipelines, Moscow, 1997, pp. 86, 87). Electrical pulses of a predetermined (depending on the gas flow rate) frequency and a fixed duration are supplied to the solenoid valve from the control unit. The disadvantage of this odorizer is the dependence of the amount of odorant in one dose on the level of odorant in the consumable container, as a result of which the odorization accuracy is low. In addition, if there are mechanical particles in the odorant, leaky closing of the electromagnetic valve is possible, as a result of which the odorant will enter the odorized gas uncontrollably.

A weight gas odorizer is also known (RF Patent RU 2317580, G05D 11/00. Published on 02/20/2008 in Bulletin No. 5) containing a supply tank, a metering pump, a pressure difference sensor, a vertical metering tube, an overpressure source, a pressure relief valve and a tightly inserted a calibrated tube with an open end missing from the lower end of the vertical measuring tube from the top into the vertical metering tube, and with the upper end connected to the gas pipeline and bypass valve. In a gas gas odorizer, the metering pump charges the measuring tube with an odorant from the supply tank to a predetermined level, after which by creating excess pressure in the upper cavity of the measuring tube, the odorant is fed into the gas pipeline through a calibrated tube. The amount of odorant received in the gas pipeline is determined by the geometric dimensions of the measuring and calibrated tubes, as well as the difference in pressure drops before and after the dose of the odorant is fed into the gas pipeline. An odorant enters the gas pipeline through a tube, part of which is above the odorant level in the supply tank, which excludes the receipt of the odorant into the gas pipeline by gravity.

The presence in the weight odorizer of a gas metering pump with movable structural elements, a differential pressure sensor in direct contact with an aggressive liquid reduces its reliability.

Closest to the claimed one is a method for automatically supplying a gas odorant to a gas pipeline, including supplying liquid to a gas pipeline using a measuring tank, which is periodically filled with an odorant from a supply tank and emptied into a low pressure gas pipeline by creating gas pressure pulses of variable magnitude and duration at the measured measuring point capacity by boosting its gas cushion from a high pressure gas pipeline and subsequent drainage of this cushion into a low pressure gas pipeline (RF Patent RU 2381415, F17D 3/12. Published 02/10/2010 in Bulletins No. 4). The repetition rate of gas pressure pulses is adjusted taking into account the volume of liquid in the measuring tank and the flow rate of the odorized gas.

A device for implementing this method comprises a vessel with a liquid connected by a hydroline to a measuring tank having a liquid level sensor in it, a gas reducer, regulating equipment, and pipelines connecting them, also connected to the gas pipeline with a pressure regulator installed in it, dividing it into a high gas pipeline pressure and a low pressure gas pipeline with a gas flow meter installed in the last unit, while the high pressure gas pipeline is connected to the gas pressure reducer through the first line, and the gas pipeline is low pressure is connected with the upper point of the vessel through the second line and the second hydraulic line with the lower point of the measured capacity, and the upper point of the measured capacity is located above the upper point of the vessel and connected through the third line, while the new one is that the device is equipped with a batch gas metering capacity and a control unit, the control equipment is made in the form of normally closed and normally open valves with an electric actuator, while the lower point of the vessel is connected to the lower point of the measured capacity through the hydraulic line with a normally open valve installed in it, and in the third line connecting the upper point of the vessel with the upper point of the measured capacity, another normally open valve is installed, the upper point of the measured capacity is connected through a normally closed valve to the portioned gas metering capacity, which is connected through the third normally an open valve with a gas reducer, and the control unit is connected by electric lines to the electric actuators of the valves, with a unit for measuring gas flow and with a liquid level sensor. (RF patent RU 2381415, F17D 3/12 (2006.01). Published 02.10.2010 in bulletins No. 4).

The disadvantages of the prototype are:

- the presence in the device a large number of controlled valves, including valves with movable structural elements that are in contact with the odorant;

- lack of accounting for the amount of odorant, which is in the hydraulic line connecting the measuring tank with a low pressure gas pipeline;

- lack of consideration of the temperature dependence of the odorant volume.

The disadvantages described are the reasons for the low accuracy and reliability of the prototype.

The technical result of the application of the present invention is to increase the reliability of the method of automatic odorization of natural gas and a device for its implementation due to the simplification of the design of the device, as well as improving the accuracy of dosing of the odorant by calculating its level in the supply tank, and therefore, after each dose low in the gas line pressure and measuring its temperature.

The essence of the invention lies in the fact that in the method of automatic odorization of natural gas, which includes periodically filling a measuring tank from a flow tank and then emptying it with high pressure gas into a low pressure gas pipeline through a hydraulic line, the upper point of which is located above the liquid level in the flow tank, high gas supply the pressure is carried out at a special reference point on the hydraulic line, dividing the liquid in it into two opposite in the direction of motion of the stream entering the gas pipeline low pressure and returning to the supply tank, and the amount of odorant entering the low pressure gas pipeline is calculated from the geometric dimensions of the part of the hydraulic line from the reference point to the level of its filling and the temperature of the odorant in it.

The essence of the invention also lies in the fact that the device for automatic odorization of natural gas comprises a supply tank with a bypass level indicator, a low pressure gas pipeline on which a gas flow measuring unit, a gas reducer, an electromagnetic valve, a hydraulic line, a control unit are installed, while the first input of the unit the control is connected to a gas flow metering unit, its output is connected to a solenoid valve, the gas gear inlet is connected to a high pressure source, and its output is connected to an electric to the solenoid valve, the upper point of the flow tank is connected to the low pressure gas pipeline, and its lower point is connected to the low pressure gas pipeline by a hydraulic line, the upper point of which is located above the liquid level in the flow tank, the hydraulic line connecting the flow tank to the low pressure gas pipeline is equipped with a special reference point for supplying high pressure gas and a temperature sensor connected to the second input of the control unit.

The drawing shows a device in which the inventive method is implemented.

The device comprises a supply tank 1, equipped with a bypass liquid level indicator 2, a gas reducer 3, a solenoid valve 4, a control unit 5, a gas flow measuring unit 6, a temperature sensor 7, a hydraulic line 8 connecting the supply tank to a low pressure gas pipeline 9.

The device operates as follows.

In the initial state, the supply tank 1 is filled with an odorant to the level h ₁ , determined by the bypass pointer of level 2, the inlet of the gas reducer 3 is under high pressure from a high pressure source (which can be used as a vessel with gas or the output of the pulse gas preparation device to gas distribution station, not shown in the drawing), and its output is set to a pressure greater than the pressure in the low pressure gas pipeline 9 by approximately 0.5 kgf / cm ² . The hydraulic line 8 is filled with an odorant to level c, which is the same as the liquid level in the supply tank. The gas flow measuring unit 6 measures the current flow rate in the gas pipe of any pressure 9, the solenoid valve 4 is closed, and the control unit 5 receives information about the current gas flow q from the gas flow measuring unit 6 and from the temperature sensor 7. Information about the geometric dimensions of the flow tank ( length of cylindrical portion L _i, the total length L _Ob, the diameter D and the type of bottoms) and the initial value of the level h _1, which is calculated volume of liquid in the supply tank, as well as the geometric volume section line a b 5 cc control unit are manually dressed (if necessary, a level switch can be installed on the supply tank, by which the fill level of the supply tank can be entered into the control unit automatically). Based on the presence of a gas flow rate (measured value of the current flow rate q), the control unit 5 gives a command to open the valve 4 and the high pressure gas from the outlet of the gas reducer 3 divides the liquid in the hydraulic line 8 connecting the flow tank to the gas pipeline 9 into two parts. The liquid from section a bc of the hydraulic line 8 is squeezed out into the gas pipeline 9, and the other part is returned to the supply tank, cleaning the hydraulic line of mechanical impurities each time the valve 4 is opened. The hydraulic section at the level of the supply tank can be made of transparent material to control the liquid level in the supply tank (instead of a level gauge) and its entry into the low pressure gas pipeline when valve 4 is opened.

The mass of liquid squeezed from the site a with:

where ρ _t is the odorant density at temperature t;

V _{a b} is the volume of fluid in the area a b;

V _1bc = π⋅r ² ⋅h ₁ is the volume of fluid in the section bc before odorization;

r is the radius of the pipeline hydraulic lines.

With the opening of valve 4 and the supply of a portion of an odorant of mass m _{1 a c} to the gas pipeline 9, the valve is closed. After closing the valve 4, the hydraulic line is filled with an odorant from the supply tank. The control unit 5 summarizes the current instantaneous gas flow rate received from the gas flow metering unit multiplied by the corresponding time intervals τ _i between the values of q _i and q _{i + 1} :

Over time, Q ₁ grows at

where ρ _n is the standard concentration of the odorant in the transported gas, a command is issued to open valve 4. Before opening the valve 4, the hydraulic line 8 is filled with an odorant from the supply tank in the area with mass m _{2 a c} = ρ _t ⋅ (V _{a b} + π⋅r ² ⋅h ₂ ). Section length bc: h ₂ = h ₁ -δh ₁ , where δh ₁ is the change in the liquid level in the supply tank after the first dose is supplied to the gas pipeline 9. The value of δh ₁ can be determined from the functional dependence of the liquid volume in the supply tank with known geometric dimensions on the level V = ƒ (h), calculating the derivative of this function with respect to the level at the point h ₁ :

After applying an odorant dose of mass m _{2 a c} to the gas pipeline, the control unit 5 again summarizes the current values of the gas flow coming from the gas flow measuring unit and

valve 4 opens. After giving j doses, the liquid level in the supply tank:

The volume of fluid V _{a b} at a b in the odorization process is a constant value. The volume of fluid in section bc decreases due to a decrease in the level of fluid in the supply tank. The duration of the gas pulse generated by the valve 4 is sufficient for supplying an odorant from section a c to the gas pipeline 9 and insufficient for it to enter the flow tank 1.

The density ρ _{t of} ethyl mercaptan (used as an odorant at gas distribution stations according to the WFD 39-1.10-069-2002, Regulation on the technical operation of gas distribution stations of gas pipelines) at a temperature t (in ° C) can be determined from the relations (R. Reed, J. Prausnits, T. Sherwood, Properties of gases and liquids: Reference manual / Translated from English under the editorship of B.I. Sokolov, 3rd ed., L .: Chemistry, 1982. 592 pp.):

ρ _op = 839 kg / m ³ is the reference density value of ethyl mercaptan at temperature

T _op = 293 K;

V _op is the reference value of the molar volume;

V _t is the molar volume at temperature t;

T _c = 499 ° K is the critical temperature;

ω = 0.19 - Pitzer's acentricity factor.

The proposed method and device has the following advantages compared to the prototype:

- the device in which the method is implemented has a simple design and contains only one valve in contact with a gas purified from mechanical impurities and moisture, which increases the reliability of its operation;

- the device does not contain elements with moving mechanisms in contact with the odorant;

- the described method of automatic odorization of natural gas prevents the accumulation of mechanical impurities in the hydraulic line, leading to a loss of operability of the device and, therefore, the device for implementing the method can operate without a filter;

- operating personnel can quickly monitor the normal operation of the odorizer by comparing the current values of the odorant level calculated by the controller in the supply tank with the readings of the bypass level indicator.

Claims (2)

1. A method of automatic odorization of natural gas, including periodically filling a measuring tank from a supply tank and then emptying it with high pressure gas into a low pressure gas pipeline through a hydraulic line, the upper point of which is located above the liquid level in the supply tank, characterized in that the high pressure gas is supplied to a special reference point on the hydraulic line, dividing the liquid in it into two opposite in the direction of motion of the stream falling into the low pressure gas pipeline and return growing in the supply tank, and the amount of odorant entering the low pressure gas pipeline is calculated from the geometric dimensions of the part of the hydraulic line from the reference point to the level of its filling and the temperature of the odorant in it. 2. Device for automatic odorization of natural gas, comprising a supply tank with a bypass level indicator, a low pressure gas pipeline on which a gas flow measuring unit is installed, a gas reducer, an electromagnetic valve, a hydraulic line, a control unit, while the first input of the control unit is connected to the measuring unit gas flow rate, its output is connected to a solenoid valve, the gas pressure regulator inlet is connected to a high pressure source, and its output is connected to a solenoid valve, the highest point of the flow the tank is connected to the low pressure gas pipeline, and its lower point is connected to the low pressure gas pipeline by a hydraulic line, the upper point of which is located above the liquid level in the flow tank, characterized in that the hydraulic line connecting the flow tank to the low pressure gas pipeline is equipped with a special reference point for gas supply high pressure and a temperature sensor connected to the second input of the control unit.

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